The long term goal is to devise new strategies for the treatment of nutritional diseases such as diabetes and specific inborn errors of energy metabolism. The specific aims: 1) to characterize the pharmacokinetics, metabolism, and safety of 1,3-butanediol diacetoacetate (ketone esters) in humans and its usefulness in patients suffering from pathologies which could be alleviated by therapeutic ketosis. 2) to devise a non-invasive clinical test to assess the activity ratio of pyruvate carboxylase; pyruvate dehydrogenase in the liver of normal subjects and of children with inborn errors of pyruvate metabolism or diabetes.